The Collaborative International Dictionary of English v.0.48:

Detrain \De*train"\, v. i. & t.
   To alight, or to cause to alight, from a railway train.
   [Eng.] --London Graphic.
   [1913 Webster]

WordNet (r) 3.0 (2006):

detrain
    v 1: leave a train

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "detrain":
   alight, come to land, debark, debus, deplane, disembark,
   disemplane, dock, drop anchor, go ashore, land, make a landfall,
   make land, make port, moor, put in, put into port, reach land,
   tie up, unboat